As background, reference is made to the following U.S. Patents which generally relate to packaging materials including those for holding products of unstable or chemically reactive nature, but which fail to teach or suggest the present invention:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 4,085,244 Stillman April 18, 1978 4,105,118 Williams, Jr., et al August 8, 1978 4,216,268 Stillman August 5, 1980 4,241,130 Barnes December 23, 1980 4,257,536 Hilmar March 24, 1981 4,284,672 Stillman August 18, 1981 4,322,003 Long March 30, 1982 4,698,247 Murray et al October 6, 1987 4,731,268 Murray, Jr. et al March 15, 1988 ______________________________________
In particular, none of the above-referenced documents, either individually or in any combination teaches or suggests a packaging film structure or package therefrom comprising: a first layer element comprised of a flexible barrier material and a sealant film, and a second layer element comprised of a high barrier material wherein the second layer element is positioned outwardly of the first layer element and the sealant is positioned inwardly of the flexible barrier, i.e.: (outside) second layer element/flexible barrier/sealant (inside).
Reference is also made to the commonly owned and copending application of Blemberg et al, U.S. application Ser. No. 07/458, 484, filed Dec. 28, 1989, and incorporated herein by reference. Blemberg et al relates to blended films, structures therefrom and methods of making and using them, e.g., multilayer structures wherein the layers have improved adhesion to each other. Such blended films can be usefully employed as layers in the structures of the present invention.
The packaging of organics especially organic liquids, e.g., polymer adhesive and coating systems, particularly two part systems, pose extroadinary problems for flexible packaging structures. In many cases, the organic adhesive or coating formulations contain aggressive solvents such as xylene or toluene. A particularly hard to hold series of products were found to be hardeners for two part curing systems (epoxy and urethanes). For example, products such as Stonhard, Inc. Product 128A containing xylenes, 2-ethoxyethanol and diethylene triamine and Product 120A containing diethylene triamine and m-phyenylenediamine were used in tests and were found to present problems when packaged in pouches and subjected to various storage conditions such as high humidity and/or varying temperature.
When high humidity is present moisture can penetrate some package structures and combine with the amines in the product packaged therein. In some structures, when humidity is present, moisture travels inward and the amine travels outward driven by the concentrations or chemical potential differences. In several cases, a solution is formed inside or between the layers of the structure which creates osmotic pressures causing bubbles or blisters to appear in an intermediate layer.
In adhesive laminated pouch structures, the organics, e.g., solvents, penetrate the sealant layer and attack the adhesive. This causes the structure to delaminate, thus losing the benefit of barrier and other properties built into the lamination. Tests have shown that high performance primers and extrusion lamination offer a superior means of constructing a lamination; but, by themselves still fall short of the requirements of a package for organics. Coextrusion of several layers offers a means to obtain very high bonding of layers such as in a multilayer cast or blown film; but, when metal, foil or biaxially oriented film must be used in a structure, one must generally rely on extrusion lamination and in previous structures the packages have still failed to meet the requirements for packaging organics.
Such materials as aluminum foil, oriented polyester and Barex.sup.R in some standard flexible packaging configurations were shown to offer a barrier to the organic product; but, all were prone to stress cracking, thus allowing the organic product to permeate. In high humidity storage and when amine-containing products were used, the area around the stress cracks quickly developed blisters of water and product. This was seen, for example, in a structure of polyethylene terephthalate (PET)/polyethylene/foil/primer/polyethylene. When amine-containing products were packaged, blisters formed under the PET or between the polyethylene and foil. Pouches that were stressed or abused by twisting or dropping, e.g., normal handling stresses, developed significantly more blisters than did unstressed control pouches. Stressed areas along the inside edge of pouch heat seals also showed small blisters in many structures.
Stress cracking was dramatically shown by sealing a Saran (TM, Dow, vinylidene chloride vinyl choride copolymer) coated film over the test pouches. Saran turns brown in color when contacted by an amine. When product penetrates some area of the test material and contacts the Saran layer, a brown pattern develops thus identifying the leak area.
It would therefore be desirable to have a film structure and packages therefrom which is suitable for containing organics such as organic liquids or organic solvents or products containing such organics, e.g., products containing amines, diamines, triamines, xylenes, toluene, ethoxyethanols, urethane monomers, or epoxy monomers, or the like, which do not suffer from the problems of conventional films and packages therefrom. It is an object of this invention to provide such packaging which does not suffer from the problems of conventional films and packages therefrom. It is also an object of this invention to provide a combination of materials which accomplishes the desired result of providing a unique structure having superior properties for holding such organics.
It is also an object of this invention to provide a packaging film structure and package such as a pouch therefrom comprising: a first layer element comprised of a flexible barrier material and a sealant film, and a second layer element comprised of a high barrier material, wherein the second layer element is positioned outwardly of the first layer element and the sealant is positioned inwardly of the flexible barrier, i.e.: (outside) second layer element/flexible barrier/sealant (inside). This structure has superior properties which makes it suitable for packaging for organics such as organic liquids or solvents or products containing such liquids or solvents, e.g., adhesives or coating formulations.